1. Field of the Invention
The invention relates to a method of power control for a PDA, and more particularly, to a method of power control for a PDA with a microprocessor.
2. Description of the Prior Art
Nowadays, low-polluting electric power applications are advocated and many electric appliances use electric power to operate. A reduction in the volume and the weight of electric appliances makes the appliances more convenient and portable. A PDA (Personal Digital Assistant) is a portable and popular device and can allow users to manage their schedules and to store data. Compared with a desktop or a notebook, it is more convenient for users who have to deal with computer data mobilely like sales and on-line production managers. Like other portable electric appliances, a battery is the main power supply source in the PDA, but the volume of the battery is limited in a PDA. A power control system can alert users to the exhaustion of the volume of the battery and allow users to control the consumption of the volume of the battery. For instance, users can store data, change another battery, or recharge the PDA using an external power supply before the exhaustion of the battery so that data is not lost or so that damage does not occur in the PDA due to over-discharging. In view of the above, an effective and perfect power control system is emphasized in modern industry.
In the prior art, many patents concerning power control systems for saving the power have been issued. For example, in U.S. Pat. No. 6,138,232, Shiell et al. taught a microprocessor that operates at a rate dependent upon an interrupt source and returns to On mode by detecting any interrupt of input signals. In U.S. Pat. No. 5,951,689, Evoy et al. described the circuit architecture of a microprocessor. In U.S. Pat. No. 5,581,772, Nanno et al. taught that a microprocessor and a CPU (Central Processing Unit) control a power system of a computer, but the technology is mainly management of switching an external power supply connected to a computer. The foregoing prior arts only discuss the power control system in the microprocessor instead of discussing the power control system of the whole system and the CPU.
To reduce the power consumption of a PDA in the present power control system, the power supply of the electric component can be cut or reduced when the system is in an idling state. The power control system in the PDA is capable of detecting whether input buttons, display devices, and other components are switched on. If the power control system does not detect any activity during a certain period, the power supply of the main system will be shut down temporarily. However in the prior art, the power management in the PDA is usually controlled by the CPU and assisted by the microprocessor, neglecting the feasibility of using the microprocessor to control the power management of the PDA. Therefore besides consuming a lot of system resources, the prior art method is dangerous because the large power consumption of using the CPU to control the power management of the whole system could result in over-discharging. To solve the above problem, not only can the technology of the prior art pertaining to the power control system of the microprocessor be utilized, but also the microprocessor can be used to manage the whole power control system in the PDA. Furthermore a multiplexing microprocessor is a better choice to monitor tasks of little power consumption, like a display of the system electric power or a debounce control program, simultaneously, for reducing the power consumption of the system and ensuring that the tasks of little power consumption still can work under the low power condition.
There are problems related to power management in the foregoing prior arts, and no technology discloses how to manage the power control system of the PDA with the microprocessor entirely for reducing the unnecessary power consumption.